1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly to a plasma display panel that is adaptive for evenly depositing a phosphorus layer by forming a buffer layer before the phosphorus layer is formed within a discharge cell of a rear surface substrate.
2. Description of the Related Art
Recently, Flat Panel Displays have briskly been developed, which include Liquid Crystal Displays (hereinafter ‘LCD’), Field Emission Displays (hereinafter ‘FED’), Plasma Display Panels (hereinafter ‘PDP’). The PDP among them has advantages of easy production due to its simple structure, excellence of high brightness and high light-emission efficiency, memory function, and wide viewing angle of over 160°, in addition, being realized into a large screen of over 40 inches.
FIG. 1 is a diagram representing the structure of a three-electrode AC surface discharge PDP of prior art.
Referring to FIG. 1, the plasma display panel includes a front substrate 10 on which pictures are displayed and a rear substrate 20 which is formed separate from the front substrate 10 with a designated distance. The front and rear substrates are bonded and sealed by frit glass.
The front substrate 10 includes a common sustain electrode Z, scan sustain electrodes Y, a dielectric layer 12 and a protective layer 13. The common sustain electrode Z and the scan sustain electrodes Y are arranged in pair to keep the luminescence of cells by discharges between them. The dielectric layer 12 limits the discharge current of the common sustain electrode Z and the scan sustain electrode Y and makes each of the electrodes insulated. And, the protective layer 13 prevents damage of the dielectric layer 12 and makes the efficiency of secondary discharge improved.
The rear substrate 20 includes a plurality of address electrode X, a dielectric layer 22, barrier ribs 21 and a phosphorus layer 23 of each R, G, B. The address electrode X generates vacuum ultraviolet ray by performing address discharge at areas where the common sustain electrode Z and the scan sustain electrodes Y are crossed. The dielectric layer 22 makes the address electrodes X insulated. The barrier ribs 21 are formed on one side of the dielectric layer 22 to be arranged in parallel so as to form a plurality of discharge spaces, i.e., cells.
The phosphorus layer 23 of each RGB is deposited at an area between the side surface of the barrier ribs 21, one barrier rib and another barrier rib to emit visible ray.
Also, the common sustain electrode Z includes a transparent electrode Za of ITO electrode, a bus electrode Zb made of metal and a black layer B. The black layer B is formed between the common electrode Za and the bus electrode Zb and made of a conductive material such as ruthenium oxide and lead oxide or carbon family to improve the contrast.
Further, the scan sustain electrode Y includes a transparent electrode Ya of ITO electrode, a bus electrode Yb made of metal and a black layer B. The black layer B is formed between the common electrode Ya and the bus electrode Yb and made of a conductive material such as ruthenium oxide and lead oxide or carbon family to improve the contrast.
And, a discharge gas is filled between the front substrate 10 the rear substrate 20 at a pressure of 300˜400 Torr. The discharge gas is mainly penning mixture gas and has He, Ne, Ar or their mixed gas as its buffer gas. A little of Xe gas is used as a source of vacuum ultraviolet ray which makes the phosphorus layer 23 emit light.
With the basis of the above-mentioned composition, the operation of the plasma display panel of prior art is described.
FIG. 2 is a diagram explaining the operation of the plasma display panel of prior art.
For reference, FIG. 2 is a diagram showing a rear substrate 20 in 90 angle to the front substrate for the sake of convenience of explanation.
Referring to FIG. 2, to describe the operation of the plasma display panel, the plasma display panel displays images by Address and Display Separate where a data input period and a display period are divided in time.
First of all, if a voltage of 150˜300V is supplied between the san sustain electrode Y and the address electrode X in an arbitrary discharge cell, a writing discharge is generated inside the cell that is located between the scan sustain electrode Y and the address electrode X to form wall charges on the internal surface of the corresponding discharge cell, thereby leaving the wall charges on the dielectric layer 12.
In the cells selected by such an address discharge, a sustain discharge is generated by an AC signal supplied to the common sustain electrode Z and the scan sustain electrode Y, and the discharge causes electric fields to be generated within the cell, thereby accelerating micro-electrons among the discharge cell.
The accelerated electrons collide with neutrons among the gas to electrolytically dissociate them into electron and ion, and the dissociated electron makes another collision with other neutron, thereby causing the neutrons to be electrolytically dissociated into electron and ion more and more rapidly so that the discharge gas becomes in the state of plasma and, at the same time, vacuum ultraviolet ray is generated.
The ultraviolet ray generated in this way excites the R, G and B phosphorus layer 23 to generate visible ray, and the generated visible ray is irradiated to the outside, thus the luminescence of an arbitrary cell, i.e., the displayed image can be perceived from the outside.
Each cell that forms such an image constitutes a unit cell being separated from others by minute barrier ribs 21. In case of making the plasma display panel in real, it is not easy to form unit discharge cells of 100 μm on a glass substrate.
Especially, because high resolution plasma display panel is required recently, the size of discharge cell is further decreased and because the phosphorus layer is deposited over the decreased discharge cell, there occurs a problem of the phosphorus layer being deposited unevenly.
Since the phosphorus layer is deposited unevenly, there occurs a problem that the efficiency of converting the vacuum ultraviolet ray into the visible ray and decay time, i.e., time when the phosphorus is excited and light is emitted, become un-uniform in accordance with each discharge cell.
Furthermore, since the phosphorus layer is deposited unevenly, the life span of the phosphorus is deteriorated.